Electronic devices are made up of a variety of components including, for example, transistors, resistors, capacitors and inductors. The characteristics of these components may depend on the material used to make them, the physical dimensions of the components and the operating conditions. For example, the resistance of a resistor may depend on the size of the resistor, the composition of materials used to make the resistor and the operating temperature.
During the manufacturing process, variations may occur that result in differences between the intended characteristics of a component and the actual characteristics of the manufactured component. For example, a resistor may be slightly larger or smaller than intended. Similarly, the material from which the resistor was made may not have the precise proportion of each element as was intended.
Variations that result from operating conditions may be somewhat less predictable. For example, depending on where the electronic device is being operated, the components may be subjected to varying degrees of temperature, humidity radiation and other conditions. Moreover, some of these conditions may change at relatively unpredictable rates.
To ensure proper operation of an electronic circuit, the electronic circuits typically are designed in a manner that takes these variations into account. That is, the electronic device may be designed so that it will operate properly even when the characteristics of the components vary.
In cutting edge applications, however, the degree to which a design may tolerate component variations may be limited to relatively small variations. In these applications even very small variations in the characteristics of components may have a relatively large impact on the operating performance of the electronic device. Accordingly, only components having characteristics within a specified range of acceptable values (commonly referred to as being “in specification” or “in spec.”) are used in such devices.
In some applications, reliable operation after manufacture is ensured by repetitively testing the electronic circuit. For example, tests may be run to ensure that some or all of the components in an electronic device are operating properly. In some cases, the failure of components may be traced to certain components being out of specification. Alternatively, tests may be run to verify that components are within a specified range of acceptable values. In the event the components are not within specification, the components may be replaced.
In some applications, however, out of specification components may not be easily replaced. For example, integrated circuits incorporate millions of components such as transistors and resistors. When the components in an integrated circuit are not operating within specification, the entire integrated circuit may need to be replaced. This may be a relatively expensive and impractical solution in some applications.
Accordingly, a need exists for improved techniques for making components that maintain a specified range of acceptable values after manufacture and during operation.